Tree Pollen — It’s in the Air!
It’s that time of year again — trees are blooming, which means their pollen is being blown into the air, the air we breathe. It’s easy to see the pollen — just look at any the edges of any puddle, still body of water or pool and you will see the tell-tale yellow-green film that is tree pollen. Airborne tree pollens that cause allergy are actually very small — from 10 to 90 or so microns (a human hair is between 40 and 300 microns). So when you see that green film in the water, or a cloud of pollen blown out of a tree from a strong gust of wind, or that yellow film on your just-washed car, you are actually looking at millions if not billions of grains of pollen. Trees pollinate in the Spring (there are a few exceptions, such as Mountain Cedar and Fall-Blooming Elm), which of course varies depending on how far north or south you live.
But not all pollen is created equal, and that certainly holds true when it comes to allergy. First of all, trees with colorful, sweet-smelling flowers are of little concern when it comes to allergy. They need their bright colors and strong smell to attract insects, who serve to carry the large, sticky pollen from flower to flower, fertilizing as they go.
Allergenically-important trees tend to have very dull, boring flowers. Many you would not even recognize as a flower. Their pollen travels by wind, and as such it needs to be small and light so as to maximize the travel distance. They also need to produce huge amounts of pollen, because so much it never makes it to the female flower — it winds up on your car! Tree pollen can travel many miles in the right conditions, so exposure to tree pollen is virtually guaranteed.
Pine tree pollen is one of the more notorious of pollens in terms of exposure and recognition. Pine trees do produce an incredible amount of pollen, but in terms of allergy, Pines are not considered important. Their pollen is larger than most tree pollens (Eastern White Pine pollen is about 75 microns in size), easily becomes airborne, and can travel great distances due to the unique sacs or bladders to aid in flight. But the pollen is just not very allergenic — it has low levels of proteins that are the root cause of an allergic reaction. The huge amount of pollen can certainly be an irritant, but the risk of being allergic to Pine pollen is very small. A review of over 150,000 allergy blood test results found positive Pine pollen IgE levels (the marker in the blood for allergy) in just 1% of the total. Maple (17%) and Cottonwood (14%) are examples of serious allergenic trees.
So why might someone experience allergy symptoms when they see Pine pollen everywhere? Because there are a lot of other trees that are also pollinating at the same time, that’s why. Oak, Maple/BoxElder, Birch, Ash, Elms, Hackberry, Cottonwood, Pecan, Sycamore, Cedars, Junipers and Mulberries are all known to cause allergic reactions. And while any one tree may only shed pollen for a week or two, taken all together any one type of tree may have its pollen in the air for a month or more, depending on local conditions. Many of these important trees are pollinating at the same time, so if you really want to find out what trees are giving you problems, you should get tested.
As mentioned earlier, it is virtually impossible to avoid tree pollen. But there are some things you can do reduce your exposure. Pollens of all types are lowest early in the day, before 10 am. Rain washes most pollen out of the air at least temporarily, so after a shower is a great time to get that walk in. Keep your windows closed as much as possible, and if you have been outside it is a good idea to wash your hair before going to bed so you are not lying down on a pillow you just dusted with pollen!
